Almost all of Queensland's 130 species of freshwater fish, including popular recreational and commercial species, need to move along river systems to complete their lifecycle.
Free passage for migrating native fish in Queensland rivers is critical to allow fish to:
- spread upstream
- find waterholes for drought refuge
- return from spawning grounds
- repopulate areas following drought
- return upstream after being washed downstream during floods
- access to food and different habitats
Some fish species move between fresh and salt water to complete their lifecycle. This movement is termed diadromous and is undertaken by fish species such as barramundi (Lates calcarifer), Australian bass (Macquaria novemaculeata) and sea mullet (Mugil cephalus).
Most native fish species that complete their lifecycle wholly in freshwater also have a requirement for movement in the river systems. This type of movement is termed potamodromous and is undertaken by inland fish species such as golden perch (Macquaria ambigua), silver perch (Bidyanus bidyanus) and Murray cod (Maccullochella peelii peelii).
Many of Queensland´s waterways are ephemeral, meaning they only flow during the wet season. In these waterways fish are stimulated to move during flood conditions, with the periods after the flood peak being the most important time for fish movements.
Freshwater fish species are also required to move between waterways during flood times to repopulate areas after drought and to create genetic variability between streams to prevent inbreeding.
Due to the dry climatic conditions, Australian native fish have limited opportunities to move, so any delay or blockage to this movement significantly reduces their long-term viability. Waterway barriers can therefore reduce native fish populations.